Refurbishing the front air pin block on my Monotype caster required, among other things, removing the two sets of tongs that operate the matrix and air pin jaws. Each of these tongs has a pivoted mounting post that is fixed on the caster table, and together they share a third post whose reciprocating motion opens and closes the tongs as needed. The tongs are held down on these posts by a washer and nut, and although I have always known that the washers have a small notch to allow the pivot point to be oiled, it is only today that I realized that these washers have a distinct top and bottom. The notch for oil is, for lack of a better word, tapered, so that it reaches closer to the central hole on the underside.
Now I’ll have to check the washers on the rear tongs to make sure they’re installed the right way up!